Field of the Disclosure
The technology of the disclosure relates to optical fiber-based distributed antenna systems (DASs) for distributing radio frequencies (RFs) and other signals over optical fibers.
Technical Background
Wireless communications are rapidly growing, with ever-increasing demands for high-speed mobile data communications. As an example, so-called “wireless fidelity,” or “WiFi” systems and wireless local area networks (WLANs), are being deployed in many different areas. Distributed antenna systems (DASs) communicate with wireless devices called “clients,” which must reside within a wireless range or “cell coverage area” of the DAS in order to communicate with an access point device. DASs can include analog and digital communications protocols and signals.
One approach to deploying a DAS involves the use of radio frequency (RF) antenna coverage areas. Antenna coverage areas can have a radius in a range from a few meters up to twenty meters, as an example. Combining a number of access point devices creates an array of antenna coverage areas. Because the antenna coverage areas each cover small areas, there are typically only a few users (clients) per antenna coverage area. This allows for minimizing the amount of RF bandwidth shared among the users of a wireless system. It may be desirable to provide antenna coverage areas in a building or other facility to provide DAS access to clients within the building or facility. However, it may be desirable to employ optical fibers to distribute communications signals. Benefits of employing optical fibers include increased bandwidth.
One type of DAS, called “Radio-over-Fiber” or “RoF,” utilizes RF signals sent over optical fibers to create antenna coverage areas. Such systems can include a head-end unit (HEU) optically coupled to a plurality of remote units (RUs) that each provide antenna coverage areas. The plurality of RUs can each include RF transceivers coupled to an antenna to transmit RF signals wirelessly, wherein the plurality of RUs are coupled to the HEU via optical fiber links. The RF transceivers in the plurality of RUs are transparent to the RF signals. The plurality of RUs convert incoming optical RF signals from an optical fiber downlink to electrical RF signals via optical-to-electrical (O/E) converters, which are then passed to the RF transceivers. The RF transceivers convert the electrical RF signals to electromagnetic signals via antennas coupled to the RF transceivers provided in the plurality of RUs. The antennas also receive electromagnetic signals (i.e., electromagnetic radiation) from clients in the antenna coverage area and convert them to electrical RF signals (i.e., electrical RF signals in wire). The plurality of RUs then convert the electrical RF signals to optical RF signals via electrical-to-optical (E/O) converters. The optical RF signals are then sent over an optical fiber uplink to the HEU.
Design, installation, and subsequent modification of DASs present significant challenges, including limited expansion and scaling capabilities, and limitations regarding compatible technology protocols. These problems are exacerbated when a DAS is intended to provide both analog and digital communications and data signals across the system. For example, many conventional solutions require providing multiple optical and electrical cable connections between a HEU and each RU of a DAS. Thus, expanding bandwidth and a number of channels between the HEU and RUs can require extensive redesign and routing of additional optical and electrical cables throughout the system. Accordingly, a DAS and related components that permit scalability and compatibility with a wide array of different technologies, without extensive reconfiguration of the entire system, may be desirable.